Method and apparatus for heating metal objects



March 24, s. F KEENER IETAL METHOD AND APPARATUS FOR HEATING METAL OBJECTS Filed April 18, 1940 5 'Sh e ets-Sheet 1 j Bnnentors JA MES H-HOPKINS5 5AM E KEENER Marcli 24, 1942. s, KEE EI-AL 2,277,592

METHOD AND APPARATUS FOR HEATING METAL OBJECTS.

Filed April 18, 1940 5 Sheets-Sheet 3' I inventors JA M E5 H. HbPKINS 80 SAM. F. KEENER F zttox neg Mardl 241, 1942- s. F. KEENER ETAL 52 5 I METHOD AND APPARATUS FOR HEATING METAL OBJECTS I 5 Sheets-Sheet 4 Filed A ril 18, 1940 l'mventors JAMES HHOPKINSb 5AM F. KEENER ttorneg March 24 1942. s KEENER AL 2,277,592

METHOD ANPAPPARATUS roR- HEATING METALOBJECTS Filed April 18, 1940 5 Sheets-Sheet 5 .II'AM s H.HoPK|Ns ac 5AM F. K ENER Patented Mar. 24, 1942 METHOD AND APPARATUS For; nna'rnvc METAL osmc'rs Sam F. Keener, Salem, and James H. Hopkins, Alliance, Ohio, asslgnors to Salem Engineer-in Company, Salem, Ohio, a proprietorship Application April 18, 1940, Serial No. 330,292

19 Claims. "(01. 263-15) This invention relates to an improved method and apparatus for heat treating ingots and-other objects of aluminum and other non-ferrous metals preparatory to their utilization in rolling and other processes and the primary object of the invention is the provision of a novel heating method and an improved furnace for carrying out the method whereby the ingots and objects may be uniformly heated in less time and at less cost than is possible by the use of methods and furnaces heretofore employed for the purpose. The function of the apparatus with which the invention is concerned is the uniform heating of the metal throughout its entire mass andthe heating of the inner portions of the ingots and objects must be accomplished by conduction from the outer surfaces thereof at a rate determined by the temperature differential existent between suchsurfaces and inner portions. An eiflcient heating method will therefore require that the outer surfaces of the pieces or ingots bemaintained at a reasonably high temperature and this presupposes that the rate of heat absorption ciently high rate of heat absorption due to the reflective power of the metal. The specular nature .of the metal turns back the major part of the radiant energy impinging on its surface, thus mitigating from the efliciency of the process and rendering diflicult the control of the furnace. Also, as it is impractical to expose all surfaces of the objects to the radiant energy sources, one

the heat absorbed by any surface must be less than the capacity of the adjacent metal to con-- duct it away as otherwise the metal at the surface will melt and flow. If an attem t is made to force the heating, one side of th objects may melt while the other side is comparatively cool. The present invention seeks to overcome the above mentioned deficiencies in present heating practice as related to aluminum and other non-ferobjects of such metals in which convection solely is relied on to transfer the heat to the same. A number of deflnite advantages, to be hereinafter explained, result from the adoption of the stated principle for non-ferrous metal heating.

Heat transfer by convection is determined by the character of the flow of the fluid transferring the heat, the surface conductance of the object being heated, and the total amount of fluid flow or convection units impinged on the object. It, is another object of the present invention to employ a convection type furnace for heating ingots, blooms, billets, castings and the like and to incorporate an arrangement within the furnace which willbe operative to distribute the fluid flow in such manner that substantially equal large volumes of fluid at the same temperature will be impinged against each of the objects, whereby the objects will be more rapidly and uniformly heated. Another object of the invention is the provision in a convection type metal heating furnace of an arrangement whereby the flow of fluid relative to the metal objects will have substantial components normal to the outer surfaces of the same. It has been found that the efficiency of. convection heating isdetermi-ned in part by the type of fluid flow with a-minimum of heat transfer occurring when the flow is purely laminar and parallel with the conducting surface and with a maximum of heat transfer when the Y flow is directly against the'surface.

-This is accomplished, in accordance with the surface or .side of the objects is invariably subjected to more energy than the other surface .or side resulting in uneven and slow heating. The control of the apparatus must be such that present invention, by lining the heating, furnace and the convection fluid flues with either hard glazed brick or metal sheets having high heat resisting properties; such as chrome alloy sheets. With this construction itis possible to employ very high velocities of fluid flow in the furnace without any errosive effect on the inner walls a rapidly accumulate in quantity and have a very rous metals by employing a heating furnace for destructive effect on the furnaceand objects pothe metal.

that by maintaining the fluid streams substantially free of abrasive particles the objects will be maintained in a clean and bright condition, thereby preventing particles from being subsequently rolled into or otherwise embedded in By employing high velocities large quantities of uniformly heated fluid may be supplied to the furnace per unit of time and by maintaining the temperature of the fluid just slightly below the melting point of the metal the heating may be accomplished at the maximum rate with safety.

These and other objects and advantages of the invention will become apparent from a consideration of the following detailed specification 'sitioned therein. Also, it should be apparent and the accompanying drawings wherein there is specifically disclosed a preferred embodiment of the invention.

In the drawings:

Figure l is a vertical section of a metal heating furnace constructed in accordance with the present invention;

Figure 2 is a horizontal section of the furnace of Figure 1;

Figure 3 is a plan'view of a representative installation of a group of the furnaces;

Figures 4 and 5 are horizontal and vertical views of a modification of one of the elements of the furnace of Figures 1 and 2;

Figure 6 is a fragmentary vertical section of a modified form of furnace constructed in accordance with the teachings of the invention;

Figure '7 is a horizontal sectional view of a modifled form of fluid distributing or collecting duct which may be incorporated in the furnace of the invention; and

Figure 8 is a vertical section of a further modified metal heating furnace constructed in accordance with the invention, the modification illustrating the representative manner in which the direction of flow of convection heating fluid through the furnace may be reversed.

The illustrated preferred embodiment. of the apparatus capable of carrying out the method of the invention includes a circular heating chamber or furnace having an annular side wall Ill, a hearth H and a removable cover [2. A portion of the annular wall In and preferably the lower part thereof is of increased diameter as indicated at l3 to privide an annular fluid distributing duct I 4 about the furnace. The furnace proper is below the operating floor l5 and a cover crane it running on rails I! built into the floor is employed to lift and remove the cover l2 for charging the ingots or removing the ingots from the surface. As indicated in Figure 3 of the drawings, one crane may service a battery of furnaces.

An outlet I3 is provided in the hearth l'lsubstantially centrally thereof and is connected with a flue-l9 which leads toa mixing chamber 20. Adjacent one wall of the mixing chamber 23 is a combustion chamber 2|, the two chambers being separated by checkerwork 2,2. One -or more fuel burners 23 discharge into the chamber 2| and upon complete combustion the gaseous prod ucts pass into the chamber 20, the checkerwork tor 28, is located in the chamber 24 and is operative to withdraw the air and gases from the furnace through the outlet l8, flue l9, chamber 20, and to force the same through the flue 28 into the distributing chamber H.

.Separating the annular distributing duct I4 from the principal space within the furnace is a circular wall 30, which may be of metal plate or sheathed brick construction and in which is provided a plurality of circumferentially spaced ports 3|. Each of the ports is provided with a door or vane 32 pivotally mounted on a vertical pivot adjacent the clockwise edge of the ports 3!, as viewed in Figure 2 of the drawings. Each of the vanes 32 is arranged to be adjustably rotated about its pivot and to be held in its adjusted position by a hinge rod 33 which extends upwardly through the upper wall of the annular chamber H where it may be engaged by a suitable operating tool 34. By referring to Figure 2 of the drawings it will be observed that the flue 26 enters the chamber l4 substantially tangentially thereof and therefore the air and gaseous products of combustion coming into the chamber from the flue at high velocity will swirl through the duct I4 in a clockwise direction as viewed in the figure. Since the outer free ends of the vanes 32 are presented to the fluid stream, the amount of the fluid diverted into the respective ports 3| will be determined by the angular position of the adjacent vanes. It is possible to so adjust the various vanes that the amount of fluid passing through each ofthe ports 3| will be equal. This is accomplished by substantially closing off the port closest to the point of entry of the fluid stream and progressively adjusting the vanes 32 outwardly clockwise about the furnace.

The invention contemplates that the interior surfaces of the furnace proper, flues l9 and 26 and chambers 20 and 24, belined with a metallic sheathing having high heat resisting properties, as chrome alloy sheets; with a hard surfaced glazed brick having sufficient abrasion resisting properties to prevent spawling and breaking off, or with other material which is suitably heat resisting and substantially free from abrasive particles which may be removed therefrom during operation of the furnace. Blower 21 and 22 assisting in the completion of the combustion.

Adjacent the chamber 23 opposite the combustion chamber 2| is a blower chamber 24 which is separated from the chamber 20 by the checkmotor .28 are of sufficient capacity and the flues l9 and. are of sufficient size to enable very large volumes of the convection heating fluid, in this case air and-gaseous products of combustion, to be circulated thIOPgh the furnace per unit of time. In certain instances of actual practice it is contemplated that the furnace and its ancillary equipment will be so designed that the fluid within the furnace may be charged up to twenty or thirty times per minute. The velocities required are of cyclonic proportions and result in very rapid charge of the fluid impinging on the metal objects and consequently heating thereof at the maximum rate. While the furnace described above is particularly suited for the heating of ingots of aluminum and other non-ferrous metals it shouldbe apparent that it is equally adaptable to the heating of blooms, billets, castings and other non ,.-which may be charged as such, depending on the size and character of the objects to be heated.

Ingots are generally stood on end on the hearth 76 and preferably arranged in ring formation. as

ticles of a sand seal.

' system remote from the chamber 2!.

shown, and the same is true of other. objects and racks containing objects but it should be understood that the material charged may be disposed in any manner due to the entire coverage of the chamber with high velocity convection currents. The racks or containers supporting the smaller objects are preferably perforated or of open construction to permit the convection currents to flow freely around the objects.

After the furnace is charged the cover 12 is applied, a liquid seal being employed for the cover to avoid the presence of the abrasive par- The circulating blower and the burner or burners 23 are now operated andthe air and gaseous products of combustion within the system are movedat high velocity successively through the ports 3|, about the ingots 36 shown or other objects, through the flue I9, chambers 20 and 24, through the blower wheel 21 and back to the distributing chamber H er or burners 23. The temperature of the fluid stream is maintained by passing the high temperature products of combustion or make 41p from the combustion chamber 2| directly into the fluid stream through the checkerwork 22. In the event that the looseness of the cover I? and other fittings of the furnace is not suiiicient to permit a volume of fluid equal to the "makeup" volume to be displaced from the system, an exhaust port may be provided anywhere in the For efflciency of operation the exposed walls and flues of the apparatus are preferably built up of insulating brick.

Referring now to Figure 2 of the drawings, it should be observed that, as the streams are diverted through the ports 3| by the vanes 32 onto the objects or racks standing on the hearth, the streams will impinge on the same substantially at right angles to the surfaces first encountered and will be reflected back and forth between the same. This, together with the high velocities used, will result in very turbulent flow of the fluid through the heating chamber which, as is well known, will result in maximum transfer of heat to the metal surfaces.

The above specificallydescribed embodiment of the invention should be considered as illustrative only since many changes may be'made therein without departing from the spirit or scope of the invention. For example, it is conceivable that equally eficient or better results may be obtained by positioning the annular distributing duct intermediate the top and bottom of the heating chamber instead of at the bottom of the chamber, as shown in the drawings. Also, the method and apparatus of the invention is independent of the type or kind of heat input means employed. The convection air stream may be maintained at its predetermined temperature by discharging the products of gaseous or liquid fuel combustion directly into the stream, as shown,:

by employing a conventional heat exchange apparatus in the flues, by electric resistance heat indicated at 42 in Figures 4 and 5, to provide fora vertical as well as a lateral diversion of the fluid stream from the duct It. This would aid the dispersion of the fluid over the length of the ingots placed on the hearth ll.

While in the furnace shown in Figures 1 and 2 the convection heating fluid is shown as being circulated from the annular distribution chamber through the heating compartment and out through the outlet l8, it should be obvious that the direction of flow of the convection heating fluid may be reversed. "Thus the convection heating fluid may be caused to enter the furnace centrally thereof and move radially outward through; the heating compartment, through the openings 3!, into the duct I. If desired, a distributing apparatus, such as shown generally at 50 in Figure 6, may be employed to deflect the heating fluid coming through the centeropening of the furnace'downwardly and outwardly against the objects supported on the hearth of the furnace. Apparatus 50 may consist simply of a perforated tube or of a series of vertically spaced frusto-conical deflectors 5|, as shown.

.The function of the apparatus is to distribute the fluid coming into the furnace .circumferentially and vertically throughout the furnace.

It is also contemplated, in accordance with the present invention, that the furnace of the invention may be operated in a reversing manner, i. e.,

the heating fluid may be circulated in the direcsired, thus further increasing the efliciency of the furnace and the uniformity of the heating thereof. This'method is particularly advantageous if the furnace is densely charged with a multiplicity of small objects, such as forgings or castings, as a more uniform heat may be acquired in a short length of time. The reversing of the direction of the heating fluid flow may be accomplished either by employing a reversible propeller'in the place of the squirrel cage type blower shown or by employing parallel duets with blowers therein arranged for fluid propulsion in opposite directions and diverter valves at the ends of the parallel ducts to direct the fluid flow to one or the other of the ducts depending on the direction of flow of the fluid.

Referring to the modification illustrated in Figure 8, a fan or propeller 61 is arranged in the duct It, being carried by a shaft 62 which extends longitudinally and centrally of the duct. Shaft, 62 is driven by a reversing motor 63 whose operation is controlled by a reversing I switch fi ial-ranged either for manual or automatic pe+ of the direction of flow of the convection heating fluid. It should be obvious, of course, that the reversing feature-is applicable 'in other specific types of furnaces, as for example, the type utilizing the involute duct 60 (Figure 'l) Figure 7 illustrates a modified form of furnace decreasing cross-sectional area in a direction away from the flue 26 and it is possible, by carefully calculating the fluid flow through the furnace, to make the fumaceheat properly and uniformly without the necessity of incorporating the louvres 32. In this case the distribution would be efiected by the decreasing cross-sectional area of the involute annular duct 80. Conversely, when the fluid is circulated through the fumace in the opposite direction, the duct 60, which then serves as a collecting duct, will operate to insure the proper distribution of the fluid coming into the furnace through the center opening.

It should now be apparent that we have provided a method and apparatus which accomplishes the objects initially set out. The ingots and other objects may be uniformly heated throughout their entire masses in the shortest possible length of time at low cost and without injury thereto, the latter resulting from the precision control which may be maintained over the heating process. The apparatus required is simple in construction and may be operated with a minimum of attention and maintenance. The in-' vention places no limitation on the size of the ap-. paratus involved. The furnaces may be either large or small.

Reference should be had to the appended claims in determining the scope of the invention.

What we claim is:

1. A metalheating furnace comprising in combination a substantially circular heating chamber having an encircling duct for the passage and distribution of convection heating fluid, a wall having a plurality of circumferentially spaced ports separating said chamber from said duct, a flue leading to said duct substantially tangential thereto, a second flue leading from said chamber at the center of the bottom-.wall thereof, means to connect said first and second mentioned flues, means to circulate convection heating fluid through said flues, duct and chamber at high velocity, means in one of said flues 3. A furnace for heating metal objects comprising in combination a substantially circular heating chamber having an annular hearth therein upon which the objects are adapted to be supported, an annular duct encircling said heating chamber and separated therefrom by a wall, a plurality of circumferentially spaced ports separating said chamber from said duct, and positioned substantially horizontally opposite the positions normally assumed by said objects on said hearth, a flue for the passage of convection heating fluid connected with said duct substantially tangential thereto, a second flue connected with the opening in said hearth, means to con-, nect said first and second mentioned flues, means to circulate convection heating fluid through said flues, duct and chamber at high velocity, means to heat said fluid at a point remote from said chamber and means to control the amount of convection heating fluid passing through each of said ports.

4. A Iumace for heating metal objects comprising in combination a substantially circular heating chamber, an annular hearth in said chamber adapted to support a plurality of said objects, a'duct encircling said chamber, a wall having a plurality of circumferentially spaced ports separating said chamber from said duct, a flue extending downwardly and outwardly from the center of said hearth, a second flue leading to said duct, means to connect said first and second mentioned flues, means to circulate convection to heat said fluid, and a pivotally mounted vane associated with each of said ports to deflect a selected volume of said fluid through the respective ports, said vanes being each adjustable about 'an axis extending normal to the direction of fluid flow through said duct.

2. A metal heating Iumace comprising in combination a substantially circular heating chamber, an annular duct encircling said chamber, a wall lfiving a plurality of circumferentially her at high velocity, means to heat said fluid,

and an adjustable closure associated with each of said ports to allow a selected volume of said fluid to pass through the respective ports.

heating fluid through said flues, duct and chamber at high velocity, means to heat said circulated convection heating fluid, and means to control the volume of fluid passing through each of said ports. 7

5. Apparatus according to claim 4 further includingmeans to reversethe direction of flow of the heating fluid through said chamber.

6. A furnace of the convection type for heating metalobjects comprising in combination a sub-.

stantially circular heating chamber, an annular hearth in said chamber and adapted to support a plurality of said objects, a plurality of circum-- ferentially spaced ports in the side wall of said chamber, andpositioned substantially horizontally opposite the positions normally assumed by said objects on said hearth, a flue extending downwardly and outwardly from the center of said hearth, means to conduct convection heating fluid to said chamber through said ports, means to control the' amount of fluid passing through each of said ports, means to connect said flue and said flrst mentioned means, a power driven blower to recirculate convection heating fluid through said flue, first mentioned means,,

ports and chamber, and means to heat said fluid.

7. A furnace of the convection type for heating metal objects comprising in combination a substantially circular heating chamber, a hearth in said chamber for the support of a plurality of said objects, a flue for the passage of convection heating fluid from said heating chamber, a plurality of circumierentially spaced ports in the side wall of said chamber, and positioned substantially horizontally opposite the positions normally assumed by said objects on 'said hearth, means to conduct convection heating fluid to said ports, means to controljthe volume of fluid passing through each of saidyports, means to connect said flue with said first mentioned means, a

spaced ports in said wall,'a passageway connecting said flue with said duct, means in said passageway to circulate convection heating fluid through said passageway, duct, chamber and flue, means in said passageway to heat said fluid, and a curved deflector associated with each of said ports to deflect fluid from said duct inwardly and upwardly against the objects positioned on said hearth.

9. A furnace for heating metal objects comprising in combination a circular heating chamber, an annular hearth in said chamber, a plurality of circumferentially spaced ports in the side wall of said chamber, a passageway for convection heating fluid leading to said ports, a flue extending downwardly and outwardly from the center opening of said hearth and connectedwith said passageway, a combustion chamber adjacent said passageway, checker'work separating said combustion chamber from said passageway,

a fluid circulating means in said passageway and being operative to circulate the convection heating fluid through said passageway, ports and flue and means to control the flow of fluid through said ports.

10. A heating furnace for objects of aluminum the top of said chamber, a wall having a' plurality of spaced ports therein separating said I chamber from said duct, said ports being positioned substantially horizontally opposite the positions normally assumed by said objects on said hearth, a flue connected with said passage, a second flue connected with said duct, means 'to connect said first and secondmentioned fiues,

means to circulate convection heating fluids.

through said flues, chamber and duct at high velocity, andmeans outside of said chamber to heat said circulated convection heating fluid.

14. The method of uniformly heating ingots and other objects of aluminum and other nonierrous metals which consists of subjecting said ingots and objects to large volumes of rapidly moving convection heating fluid issuing from a multiplicity of points surrounding the ingots and objects, withdrawing the fluid from a point below the ingots and objects, recirculating said fluid, and maintaining said fluid .at a uniform and other non-ferrous metals comprising in combination a heating chamber, a hearth in said chamber for the support of a plurality of said objects, a removable cover for said chamber, a flue extending downwardly and outwardly from said chamber, openings in the side walis of said chamber horizontally opposite said objects and spaced substantially from said cover for the passage of convection heating fluids thereinto and against the sides of said objects, means to connect the outer end of said flue with said openings, means to recirculate said heating fluid at high velocity through said chamber, flue and openings, and means remote from said chamber to heat said fluid.

11. A furnace for heating metal objects comtemperature lower than the fusion temperature of the metal of the ingots.

15. The method of uniformly. heating ingots and other objects of aluminum and other nonferrous metalsv which consists of arranging said ingots or objects about a central point and subjecting said ingots or objects to large volumes of rapidly moving convection heating fluid flowing laterally between said point and a multiplicity of points spaced radially outward with relation to said central point and circum'ferentia'lly with respect to each other, recirculating said fluid, and

maintaining said fluid at uniform temperature lower than the fusion temperature of the metal of the ingots.

16. A furnace of the convection type for heating metal objects comprising in combination a substantially circular heating chamber, an annular hearth in said chamber for the support of a plurality of said objects, a removable cover for said chamber, a plurality of circumferentially spaced ports in the side wall of said chamber positioned substantially horizontally opposite the positions normally assumed by said objects on said hearth and spaced substantially from said prising in combination a substantially circular heating chamber, an annular hearth in said chamber adapted to support a plurality of said objects, an involute duct encircling said chamber,

- a wall having a plurality of circumferentially spaced ports separating said chamber from said duct, a flue extending downwardly and outwardly from the center of said hearth, a second flue connected with said duct, means to connect said first and second mentioned flues, means to circulate convection heating fluid through said flues.

duct and chamber at high velocity, and means cover, a downwardly and outwardly extending flue connected to the center opening in said hearth, means to connect said ports and flue, a power driven blower to recirculate convection heating fluid through said means, ports, fiue,'and chamber, and means to heat said fluid at a point removed from said chamber.

17. A convection type heating furnace for objects of aluminum and other non-ferrous metals comprising in combination a heating chamber, a hearth in said chamber for the support of a plurality of said objects, a removable cover for said chamber, openings in the walls'of said chamber horizontally opposite said objects and spaced substantially from said cover for the passage of convection heating fluid, a duct connected with the lower central portion of said chamber, means to connect said duct with said openings, a power driven blower to recirculate the fluid through said chamber, means, and duct at high velocity,

and means remote from said chamber to heat nular hearth in said chamber for the support of i a plurality of said objects. a removable cover for said chamber, a plurality of circumferentially spaced ports in the side wall of said chamber spaced substantially from said cover, a downwardly and outwardly extending flue connected tothe center opening in said hearth, means to connect said ports and flue, a power driven 

